Abstract:

A compressor has a suction port, a discharge port, and an economizer port.
A condenser is downstream of the discharge port. An evaporator is
upstream of the suction port. An expansion device is between the
condenser and the evaporator. An economizer is between the condenser and
the evaporator. An economizer line extends from the economizer to the
economizer port. A resonator is located in the economizer line and has a
first branch and a second branch. A first flowpath length across the
resonator through the second branch is longer than a second flowpath
length across the resonator through the first branch.

Claims:

1. An apparatus comprising:a compressor (22) having a suction port (46), a
discharge port (48), and an economizer port (44);a condenser (24)
downstream of the discharge port;an evaporator (28) upstream of the
suction port;an expansion device (30) between the condenser and the
evaporator; andan economizer (40) between the condenser and the
evaporator, an economizer line (42) extending from the economizer to the
economizer port, wherein:a resonator (60) is located in the economizer
line and has a first branch (66) and a second branch (68), a first
flowpath length across the resonator through the second branch being
longer than a second flowpath length across the resonator through the
first branch

2. The apparatus of claim 1 wherein:the first branch is straight; andthe
second branch has first (70) and second (72) nonparallel legs.

3. The apparatus of claim 1 wherein:the first and second branches have
essentially identical effective cross-sectional areas.

4. The apparatus of claim 1 wherein:the compressor is an electric screw
compressor.

5. The apparatus of claim 1 wherein:the first flowpath length is longer
than the second flowpath length by 0.2-0.4 m.

6. The apparatus of claim 1 wherein:there is no absorptive muffler along
the economizer line.

7. An apparatus comprising:a compressor (22) having a suction port (46), a
discharge port (48), and an economizer port (44);a condenser (24)
downstream of the discharge port;an evaporator (28) upstream of the
suction port;an expansion device (30) between the condenser and the
evaporator; andan economizer (40) between the condenser and the
evaporator, an economizer line (42) extending from the economizer to the
economizer port, wherein:means (60) are located in the economizer line
for wave canceling vibrations propagating along the economizer line.

13. The apparatus of claim 7 wherein:there is no absorptive muffler along
the economizer line.

14. A method for remanufacturing a refrigeration system (20) or
reengineering a configuration of a system, comprising:placing a resonator
(60) in an economizer line (42) so as to divide a flowpath through the
line into first and second fluidically parallel sections, the second
section being longer than the first.

16. The method of claim 14 further comprising:selecting a difference in
flowpath length through the first and second sections to provide a
pulsation cancellation.

17. The method of claim 14 wherein:the selecting comprises an iterative
process of varying the difference and determining an associated sound
level.

18. The method of claim 14 wherein:the second section is 0.2-0.4 m longer
than the first section.

19. The method of claim 14 wherein:the first and second sections have
essentially identical effective cross-sectional areas.

20. The method of claim 14 wherein the system has:a compressor having a
suction port, a discharge port, and an intermediate economizer port;a
condenser downstream of the discharge port;an evaporator upstream of the
suction port;an expansion device between the condenser and the
evaporator; andan economizer between the condenser and the evaporator,
said economizer line extending from the economizer to the economizer
port.

21. An apparatus positioned along an economizer line located in a
refrigeration system, wherein the apparatus reduces vibrations with the
system, the apparatus comprising:a first manifold configured to be in
fluid connection to an economizer vessel;a second manifold configured to
be in fluid connection with a compressor;a first flowpath that is
substantially straight and extends between the first and second
manifold;a second flowpath that extends between the first and second
manifold, wherein the second flowpath is of a different length than the
first flowpath such that any pulsations traveling through the first and
second flowpaths are out of phase with one another upon reaching the
second manifold.

Description:

BACKGROUND OF THE INVENTION

[0001]The invention relates to refrigeration systems. More particularly,
the invention relates to sound control for economized refrigeration
systems.

[0002]In positive displacement compressors, discrete volumes of gas are:
trapped at a suction pressure; compressed; and discharged at a discharge
pressure. The trapping and discharge each may produce pressure pulsations
and related noise generation. Accordingly, a well developed field exists
in compressor sound suppression.

[0003]Often, an absorptive muffler is located downstream of the
compressor's working elements to dissipate downstream propagation of
vibrations. Exemplary mufflers may be housed within a housing structure
of the compressor. Additionally, in economized compressors, an absorptive
muffler may be located inline in the economizer line to dissipate
upstream propagation along the economizer line.

SUMMARY OF THE INVENTION

[0004]Accordingly, one aspect of the invention involves a compressor
having a suction port, a discharge port, and an economizer port. A
condenser is downstream of the discharge port. An evaporator is upstream
of the suction port. An expansion device is between the condenser and the
evaporator. An economizer is between the condenser and the evaporator. An
economizer line extends from the economizer to the economizer port. A
resonator is located in the economizer line and has a first branch and a
second branch. A first flowpath length across the resonator through the
second branch is longer than a second flowpath length across the
resonator through the first branch.

[0005]The details of one or more embodiments of the invention are set
forth in the accompanying drawings and the description below. Other
features, objects, and advantages of the invention will be apparent from
the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a schematic view of an economized refrigeration system.

[0007]Like reference numbers and designations in the various drawings
indicate like elements.

DETAILED DESCRIPTION

[0008]FIG. 1 shows a refrigeration system 20 having a compressor 22 (e.g.,
an electric screw compressor). A condenser 24 is downstream of the
compressor 22 along a primary flowpath 26 (e.g., defined by associated
refrigerant conduits/lines). An evaporator 28 is downstream of the
condenser 24 and upstream of the compressor 22 along the primary flowpath
26. An expansion device 30 (e.g., an electronic expansion valve or fixed
orifice) is downstream of the condenser 24 and upstream of the evaporator
28.

[0009]In the exemplary economized system, an economizer 40 is between the
condenser and evaporator 28 along the flowpath 26 and, more narrowly,
between the condenser 24 and expansion device 30. An economizer line 42
extends from the economizer 40 to an economizer port 44 on the compressor
intermediate a suction (inlet) port 46 and a discharge (outlet) port 48.
In operation, the compressor 22 drives refrigerant in a downstream
direction along the primary flowpath 26. An economizer flow portion may
be diverted at the economizer to pass through the economizer line 42 and
return to the economizer port 44. As so-far described, the system is
schematic and exemplary. Other components (e.g., fans, valves controlling
refrigerant flow, and the like and a control system controlling their
operation) as well as other details may be present.

[0010]In operation, pressure pulsations from the compressor 22 may pass
counterflow through the refrigerant flowing in the economizer line. When
these pulsations reach the vessel 50 of the economizer 40, the vessel 50
may resonate, emitting undesirable sound. Among prior art solutions is
the use of an absorptive muffler in the economizer line. FIG. 1, however,
shows an implementation wherein an absorptive muffler has been replaced
by a dual path resonator (e.g., a Herschel-Quincke resonator) 60. The
exemplary resonator includes first and second manifolds 62 and 64. A
first flowpath segment/section/branch 66 extends straight between the
manifolds. A second flowpath segment/section/branch 68 has first and
second legs 70 and 72 at an angle to each other. The result is that the
flowpath length through the second section 68 is longer than the flowpath
length through the first section. In an exemplary implementation, the
length difference is one half of the wavelength of a target pressure
pulsation (e.g., associated with a target operating speed of the
compressor and associated refrigerant flow conditions through the
economizer line). Thus, pulsations in the refrigerant flowing along the
two sections 66 and 68 will be out of phase upon reaching the second
manifold 64 and will cancel so that less pulsation is transmitted to the
housing 50. The exemplary first and second segments have essentially
identical effective cross-sectional areas (e.g., to pass identical mass
flows). An exemplary length difference is 0.1-1.0 m, more narrowly
0.2-0.4 m.

[0011]Although the second section 68 is shown with straight segment legs
70 and 72 at an angle to each other, other relative shapes of the two
sections 66 and 68 are possible. Although shown replacing an absorptive
muffler, the resonator may complement an absorptive muffler.

[0012]The resonator may be supplied in a reengineering of an existing
system configuration or in a remanufacturing of an existing system. The
resonator geometry may be tuned to provide the desired absorption. The
tuning may be based solely upon calculation. Alternatively, the tuning
may further reflect an iterative optimization performed on actual
hardware or on a computer simulation. The optimization may involve
selecting an initial resonator geometry and determining (e.g., measuring)
an associated output sound parameter. This may be followed by modifying
the geometry and redetermining the parameter until there is convergence
or other indication of desired result.

[0013]One or more embodiments of the present invention have been
described. Nevertheless, it will be understood that various modifications
may be made without departing from the spirit and scope of the invention.
For example, when applied as a modification of an existing system,
details of the existing system may implement details of the particular
implementation. Accordingly, other embodiments are within the scope of
the following claims.